Earth has more barrier islands, strips of sand parallel to a coast but separated from it by estuaries or lagoons, than previously thought, U.S. researchers say.
Scientists at Duke University and Meredith College used satellite images, topographical maps and navigational charts to identify a total of 2,149 of the offshore deposits of sand and sediment, a significant increase of the 1,492 counted in 2001 before the public availability of satellite imagery.
All told, the 2,149 barrier islands measure 12,913 miles in length, and are found along all the continents except Antarctica and in all oceans, a Duke release said Tuesday.
Taken together, barrier islands make up roughly 10 percent of the Earth's continental shorelines, the researchers said.
Barrier islands help protect low-lying mainland coasts from erosion and storm damage and can be important wildlife habitats.
Unlike stationary coastal land forms, barrier islands build up, erode, migrate and rebuild over time in response to waves, tides, currents and other physical processes in the open ocean environment, the researchers said.
The survey results have been published in the Journal of Coastal Research.
"This provides proof that barrier islands exist in every climate and in every tide-wave combination," Duke geology professor Orrin H. Pilkey said.
"We found that everywhere there is a flat piece of land next to the coast, a reasonable supply of sand, enough waves to move sand or sediment about, and a recent sea-level rise that caused a crooked shoreline, barrier islands exist."
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